package cn.bdqn.sptparent.common.util;

public class Base64Utils {

        static private final int     BASELENGTH           = 128;
        static private final int     LOOKUPLENGTH         = 64;
        static private final int     TWENTYFOURBITGROUP   = 24;
        static private final int     EIGHTBIT             = 8;
        static private final int     SIXTEENBIT           = 16;
        static private final int     FOURBYTE             = 4;
        static private final int     SIGN                 = -128;
        static private final char    PAD                  = '=';
        static private final boolean fDebug               = false;
        static final private byte[]  base64Alphabet       = new byte[BASELENGTH];
        static final private char[]  lookUpBase64Alphabet = new char[LOOKUPLENGTH];

        static {
            for (int i = 0; i < BASELENGTH; ++i) {
                base64Alphabet[i] = -1;
            }
            for (int i = 'Z'; i >= 'A'; i--) {
                base64Alphabet[i] = (byte) (i - 'A');
            }
            for (int i = 'z'; i >= 'a'; i--) {
                base64Alphabet[i] = (byte) (i - 'a' + 26);
            }

            for (int i = '9'; i >= '0'; i--) {
                base64Alphabet[i] = (byte) (i - '0' + 52);
            }

            base64Alphabet['+'] = 62;
            base64Alphabet['/'] = 63;

            for (int i = 0; i <= 25; i++) {
                lookUpBase64Alphabet[i] = (char) ('A' + i);
            }

            for (int i = 26, j = 0; i <= 51; i++, j++) {
                lookUpBase64Alphabet[i] = (char) ('a' + j);
            }

            for (int i = 52, j = 0; i <= 61; i++, j++) {
                lookUpBase64Alphabet[i] = (char) ('0' + j);
            }
            lookUpBase64Alphabet[62] = (char) '+';
            lookUpBase64Alphabet[63] = (char) '/';

        }

        private static boolean isWhiteSpace(char octect) {
            return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);
        }

        private static boolean isPad(char octect) {
            return (octect == PAD);
        }

        private static boolean isData(char octect) {
            return (octect < BASELENGTH && base64Alphabet[octect] != -1);
        }

        /**
         * Encodes hex octects into Base64
         *
         * @param binaryData Array containing binaryData
         * @return Encoded Base64 array
         */
        public static String encode(byte[] binaryData) {

            if (binaryData == null) {
                return null;
            }

            int lengthDataBits = binaryData.length * EIGHTBIT;
            if (lengthDataBits == 0) {
                return "";
            }

            int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
            int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
            int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1 : numberTriplets;
            char encodedData[] = null;

            encodedData = new char[numberQuartet * 4];

            byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;

            int encodedIndex = 0;
            int dataIndex = 0;
            if (fDebug) {
                System.out.println("number of triplets = " + numberTriplets);
            }

            for (int i = 0; i < numberTriplets; i++) {
                b1 = binaryData[dataIndex++];
                b2 = binaryData[dataIndex++];
                b3 = binaryData[dataIndex++];

                if (fDebug) {
                    System.out.println("b1= " + b1 + ", b2= " + b2 + ", b3= " + b3);
                }

                l = (byte) (b2 & 0x0f);
                k = (byte) (b1 & 0x03);

                byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
                byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
                byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);

                if (fDebug) {
                    System.out.println("val2 = " + val2);
                    System.out.println("k4   = " + (k << 4));
                    System.out.println("vak  = " + (val2 | (k << 4)));
                }

                encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
                encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
                encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
                encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
            }

            // form integral number of 6-bit groups
            if (fewerThan24bits == EIGHTBIT) {
                b1 = binaryData[dataIndex];
                k = (byte) (b1 & 0x03);
                if (fDebug) {
                    System.out.println("b1=" + b1);
                    System.out.println("b1<<2 = " + (b1 >> 2));
                }
                byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
                encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
                encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
                encodedData[encodedIndex++] = PAD;
                encodedData[encodedIndex++] = PAD;
            } else if (fewerThan24bits == SIXTEENBIT) {
                b1 = binaryData[dataIndex];
                b2 = binaryData[dataIndex + 1];
                l = (byte) (b2 & 0x0f);
                k = (byte) (b1 & 0x03);

                byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
                byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);

                encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
                encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
                encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
                encodedData[encodedIndex++] = PAD;
            }

            return new String(encodedData);
        }

        /**
         * Decodes Base64 data into octects
         *
         * @param encoded string containing Base64 data
         * @return Array containind decoded data.
         */
        public static byte[] decode(String encoded) {

            if (encoded == null) {
                return null;
            }

            char[] base64Data = encoded.toCharArray();
            // remove white spaces
            int len = removeWhiteSpace(base64Data);

            if (len % FOURBYTE != 0) {
                return null;//should be divisible by four
            }

            int numberQuadruple = (len / FOURBYTE);

            if (numberQuadruple == 0) {
                return new byte[0];
            }

            byte decodedData[] = null;
            byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
            char d1 = 0, d2 = 0, d3 = 0, d4 = 0;

            int i = 0;
            int encodedIndex = 0;
            int dataIndex = 0;
            decodedData = new byte[(numberQuadruple) * 3];

            for (; i < numberQuadruple - 1; i++) {

                if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))
                        || !isData((d3 = base64Data[dataIndex++]))
                        || !isData((d4 = base64Data[dataIndex++]))) {
                    return null;
                }//if found "no data" just return null

                b1 = base64Alphabet[d1];
                b2 = base64Alphabet[d2];
                b3 = base64Alphabet[d3];
                b4 = base64Alphabet[d4];

                decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
                decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
                decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
            }

            if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))) {
                return null;//if found "no data" just return null
            }

            b1 = base64Alphabet[d1];
            b2 = base64Alphabet[d2];

            d3 = base64Data[dataIndex++];
            d4 = base64Data[dataIndex++];
            if (!isData((d3)) || !isData((d4))) {//Check if they are PAD characters
                if (isPad(d3) && isPad(d4)) {
                    if ((b2 & 0xf) != 0)//last 4 bits should be zero
                    {
                        return null;
                    }
                    byte[] tmp = new byte[i * 3 + 1];
                    System.arraycopy(decodedData, 0, tmp, 0, i * 3);
                    tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                    return tmp;
                } else if (!isPad(d3) && isPad(d4)) {
                    b3 = base64Alphabet[d3];
                    if ((b3 & 0x3) != 0)//last 2 bits should be zero
                    {
                        return null;
                    }
                    byte[] tmp = new byte[i * 3 + 2];
                    System.arraycopy(decodedData, 0, tmp, 0, i * 3);
                    tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
                    tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
                    return tmp;
                } else {
                    return null;
                }
            } else { //No PAD e.g 3cQl
                b3 = base64Alphabet[d3];
                b4 = base64Alphabet[d4];
                decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
                decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
                decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);

            }

            return decodedData;
        }

        /**
         * remove WhiteSpace from MIME containing encoded Base64 data.
         *
         * @param data  the byte array of base64 data (with WS)
         * @return      the new length
         */
        private static int removeWhiteSpace(char[] data) {
            if (data == null) {
                return 0;
            }

            // count characters that's not whitespace
            int newSize = 0;
            int len = data.length;
            for (int i = 0; i < len; i++) {
                if (!isWhiteSpace(data[i])) {
                    data[newSize++] = data[i];
                }
            }
            return newSize;
        }
    }

